The aspects of the disclosed embodiments relate to the field of the propulsion of transport aircraft such as civilian transport aircraft.
More particularly, the aspects of the disclosed embodiments relate to a turbojet engine propulsive system that can perform various functions complementary to propulsion.
For reasons of optimization of propulsion and in particular for reasons of weight, in the case of current aircraft such as civilian aircraft and military transport aircraft, there are frequent attempts to use the engines employed for the propulsion of the aircraft for other functions performed by other systems, either to complement these systems or to substitute for them more or less totally.
Thus, the propulsion engines on very many aircrafts are used to supplement braking when the aircraft lands.
The jet engines provided with this capability of braking make use of a so-called thrust reverser device, which deflects the blast of the jet engine when it is deployed and creates a thrust directed toward the rear, which participates in the braking.
In the high-dilution jet engines currently common on civilian and military jet transport aircraft, the thrust reversers act only on the secondary flow, blocking the secondary stream and orienting the flow of air toward the sides and toward the front. So-called grid reversers and petal reversers are known to exist, which show only two used positions: the retracted position in which the jet engine thrust is not modified and the deployed position for which the thrust is reversed.
This configuration of reversers has the defect of not acting on the primary flow of the jet engine, which consequently continues to exert thrust toward the front, which to that extent reduces the efficacy of the reversers, unless supplementary means are utilized.
Furthermore, such reversers in the retracted position by their imperfections cause pressure losses in the stream of secondary flow, which affects the propulsive output and accordingly necessitates great design and control efforts in operation to limit the losses of output.
With single-flow or limited dilution jet engines, it is known how to use clamshell thrust reversers in which two hinged half-shells are placed behind the jet output of the jet engine.
In the retracted position of the reverser, the two half-shells are spread apart, so that the jet of the jet engine passes between the half-shells without being perturbed, and in the deployed position of the reverser, the two half-shells are brought together into contact with one another so as to block the jet of the jet engines and to deflect it to the sides, or toward the top and bottom, and toward the front.
Such an example of clamshell thrust reversers corresponds to those of the Concorde aircraft.
Although it is used less frequently, it is also known how to use a propulsion engine to function as an auxiliary power group to supply the aircraft on the ground with energy and air.
In some cases, the electrical generators and the air intakes used by the aircraft in flight are also used on the ground with the engine functioning for it when no external energy source is available.
For example, this is the case with turboprop aircraft in which one of the turbojet engines is placed in operation on the ground with the propeller immobilized by a propeller brake in a so-called “hotel mode.”
In the case of turbojet engines, it was considered replacing the auxiliary power group generally installed in the rear section of the fuselage by a turbine that has an “auxiliary power group or APU” operating mode, in particular with the aircraft parked on the ground, and a “propulsion” operating mode, in particular at takeoff or in flight.
Depending on whether this rear turbine is of small or comparable size, or greater than those of the propulsion engines, it is considered as an APU with an optional propulsive function, or as a propulsion jet engine with an operating mode as auxiliary generator.
This type of solution, which does not seem to have found application up to now on a commercial turbojet aircraft, has the drawback of requiring a turbine; in practice a jet engine, specifically adapted to this mixed function, and the solution proves to be disadvantageous from the point of view of weight balance and from an economic point of view.
Accordingly, the current solutions are limited in use, and their performance is adversely affected by the weight balances and unfavorable outputs, and by the complex and costly installations.